The present invention relates to a method and a system for manufacturing wafer-like slices from a body of a substrate material, especially for use in the manufacture of semiconductor devices.
Typically, the substrate material is silicon or other semiconductor material, alone or in combination with other materials.
Conventional methods and systems for manufacturing wafer-like slices from a body of a substrate material use sawing machines to cut the body by abrasion into slices. The substrate material in the saw kerf is disintegrated into powder.
There are two different principles for cutting the body of substrate material into wafer-like slices.
One of the two principles (A) combines smooth wires pulled through the hard substrate material while abrasive slurries composed of a viscous liquid (e.g., polyethylene glycol or mineral oil) and abrasive solid particles (e.g., silicon carbide) provide the means for abrading the substrate material in the saw kerf and additionally act as coolant and lubricant as well as carrier for the disintegrated powdery substrate material.
The other principle (B) uses armed wires which are equipped on their surface with abrasive particles, e.g., diamond particles. An aqueous fluid, typically drinking water, is applied for cooling and lubrication. It also serves as a carrier for the disintegrated substrate material. The armed wires have a larger diameter than the smooth wires used according to principle (A). Therefore, the saw kerf resulting in principle (B) is wider than in principle (A).
The general disadvantage of both principles is the substantial loss of valuable substrate material. In many cases, the saw kerf is approximately as wide as the remaining slices. Hence, about 50% of the valuable material is ground into powdery particles, and only 50% remain as solid wafer components or slices which may be used to produce, e.g., silicon wafers for photovoltaic cells and integrated semiconductor circuits. In view of the high purity and the high costs of many of the substrate materials, this loss results in an enormous waste of material and is also a potential source for environmental pollution.
Principle A further suffers from the contamination of the abrasive slurry that is circulated in the system by ground substrate material (so-called kerf loss), metal traces of the wire and the fines of the abrasive material itself generated by wear. As the degree of contamination of the abrasive slurry grows over time, the efficiency of the sawing operation decreases. When the slurry finally becomes ineffective or exhausted, it is drained from the system and must be discarded and replaced by new slurry or sent to a regeneration process prior to re-use. Moreover, the viscous, spent, contaminated slurry sticks to the wafer surfaces and complicates the cleaning of the wafers after cutting.